Machines of this type and suitable for forming walls are already known.
For example, U.S. Pat. No. 3,893,302 describes a machine and method for excavating trenches and constructing walls in the excavated trenches.
That machine comprises a cutter tool located in the front portion of the machine, in the form of an endless chain of excavation buckets.
The rear portion of the machine has a vertical duct for delivering concrete from a container situated outside the trench to the rear of the machine in order to fill the trench that has just been dug.
Pumping concrete into the trench creates hydrostatic pressure on the rear portion of the machine, thereby exerting driving thrust in the excavation direction.
However, that machine is subjected to the hydrostatic pressure of the concrete and, in any event, no means are provided for controlling either the thrust force created by the pressure of the concrete on the excavator means, or the speed of advance of the machine.
It is known that the thrust force and the speed of advance of the cutter tool need to be controlled, regardless of the nature of the terrain being excavated.
In particular, the force created by the hydraulic pressure is usually greater than the force needed for applying pressure to the cutter tools.
It will therefore be understood that it is necessary to control the speed of advance of the machine and also the thrust force on the cutter tools.
In addition, in that document, it is not possible to adapt the cutter tools to the nature of the terrain to be excavated.
In the event of it being desirable to change the cutter tool, it is necessary to change the machine, which leads to a loss of time that might paralyze progress on a building site.
Finally, the machine described in that document is capable solely of forming diaphragm type walls, whereas in certain situations it can be advantageous to place prefabricated wall elements in the trench, and to do so without needing to change the excavator machine or the cutter tool.